The operation is simple: a user types a word or phrase, Google analyzes the uk whatsapp number title and description of the products that contain it, these products enter "into the auction" just like it works for the paid results of the search network, the position of the advertisers' ads will be determined by the CPC bid of each.
You can't buy specific keywords, you'll have to work like in SEO optimization, creating titles and descriptions (on your feed) relevant to what you're promoting. There's not even a quality score like for Adwords keywords, it's the quality of the feed that allows you to be visible or not.
Is Google Shopping useful for me?
To understand if it is useful or not, you need to understand how much your products are searched for online (do an analysis with Google Adwords tools), do a research yourself and analyze who your direct competitors would be.
Keep in mind that the prices will be visible immediately after the search (see image above), so if your prices are significantly higher than your other direct competitors it will be difficult for you to be preferred to others if you do not adopt a proper communication strategy that makes you unique compared to others.